Bullet-Resistant Electrical Installation

ABSTRACT

An electrical installation, in particular a transformer, phase shifter or inductor, which includes a fluid-filled tank having side walls, wherein, for protection against bombardment and/or fragmentation effects, the side walls are formed in a bullet-resistant manner and are made of a material having a traction strength of greater than 1000 MPa, or wherein a bullet-resistant reinforcement made of such a material is provided, the outer side of which envelope the side walls.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of application Ser. No. 15/509,135filed 6 Mar. 2017, which is a U.S. national stage of application No.PCT/EP2014/002516 filed 17 Sep. 2014.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to the technical field of electricalinstallations and, more particularly, to electrical transformers, phaseshifters and inductors of high rated power, such as those commonly usedin energy distribution networks.

2. Description of the Related Art

Electrical installations, such as transformers, inductors or switchingdevices, represent node points in an energy distribution network, and intimes of crisis these node points can be potential targets of attack fordestructive strikes from outside. Such strikes include, e.g., attacksfrom surrounding terrain by fire from small arms, explosive chargesdetonated in the vicinity of the electrical installation, or evengrenade or bomb fragments. The side walls of a tank filled with fluidare particularly vulnerable, in this case. If these side walls are hitby bullets, depending on the intensity of the missile effect, a leak canoccur. However, even if the tank remains tight, a pressure wave canpropagate in a liquid-filled tank, causing safety devices to shut downthe installation. In both cases, the energy supply can be adverselyaffected by the attack.

DE 37 29 048 A1 discloses, for example, object protection for atransformer of high rated power, where the side walls of the transformertank are internally reinforced with protective plates to protect againstexternal mechanical effects. The protective plates are welded onto theside walls on the inside and consist of a special steel for cushioningfragments and missiles. One disadvantage here is that the protectivereinforcement is weakened in the region of the welded seam. A furtherdisadvantage is that, in the case of bullets, pressure waves propagatein the liquid-filled tank, which can result in the transformer beingshut down by safety devices. The energy supply is then interrupted atleast temporarily.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprotect an electrical installation in an energy distribution network, inparticular a transformer or an inductor, such that the energy supply isnot adversely affected even in the event of an attack using small armsor an explosive charge.

This and other objects and advantages are achieved in accordance withthe invention by a method for upgrading an existing electricalinstallation and an electrical installation, in particular atransformer, a phase shifter or an inductor, comprising a fluid-filledtank having side walls, where, for protection against the effect ofbullets and/or fragments the side walls are formed in apenetration-inhibiting manner and are made of a material having atensile strength R_(m) greater than 1000 MPa, or apenetration-inhibiting reinforcement made of such a material is providedand envelops the side walls on the outside.

The bullet-resistance can therefore be achieved by manufacturing atleast the side walls of the tank from, e.g., a steel having a tensilestrength R_(m) greater than 1000 MPa. However, the tank itself can bemanufactured from conventional steel and externally enveloped by areinforcement that exhibits this tensile strength. The tensile strengthof materials is defined in DIN EN ISO 6892-1.

In accordance with a fundamental idea of the invention, the objectprotection is therefore achieved by a penetration-inhibiting embodimentof the tank or the reinforcement or armor. The fluid in the tank can bea cooling fluid or insulation fluid, such as transformer oil, or a gasin a switching installation. The term bullet-resistant is understood tomean the resistance of a material or a construction to withstandpenetration by a missile under defined conditions. A definition ofmissile-resistance is provided in the American standard UL 742 (Ratingsof Bullet Resistant Materials) Level 1 through Level 10, for example.This corresponds to test levels between 1 and 14 as defined in the 2006general test guidelines of the “Vereinigung der Prüfstellen fürangriffhemmende Materialien and Konstruktionen” (VPMA APR 2006)[Association of Test Centers for Attack-Inhibiting Materials andConstructions]. Test level 1 starts with a caliber 0.22 lr, a missilemass of 2.6 g and a missile energy of approximately 160 J (Joules). Testlevel 14 comprises a caliber 14.5×114, a missile mass of approximately64 g and a missile energy of 26,308 J (Joules). Corresponding levelsbetween BR1 and BR7 are defined in the European standard DIN EN 1063.Within the meaning of the invention, this balistically definedbullet-inhibiting action against a handgun and/or rifle appliesanalogously to the fragmentation action of an explosive structure thatdetonates in the vicinity of the installation. In other words, theprotective measure in accordance with the invention comprises at least asphere of action specified in the standards cited above. In other words,the effect of bullets within such a sphere does not result in a leakoccurring in the tank of the electrical installation. A protectivemeasure within this sphere of action (Level 1 to 10, or test level 1-14)can be realized at reasonable cost. In principle, protection of anelectrical installation against bullets can also extend beyond thissphere of action.

In accordance with the invention, a material having a tensile strengthR_(m) of greater than 1000 MPa (megapascal) is used for the protectivemeasure. A high tensile strength renders the material particularlysuitable for reinforcement or armor. Such a material having high tensilestrength can be a metallic or non-metallic material, such as a polymermaterial, a carbon-fiber-reinforced synthetic material, a material thatis based on polyethylene, or aramide fibers. Known trademarks foraramide fibers include, e.g., Nomex® and Kevlar® by DuPont. In thiscase, the synthetic material fibers can be woven together and realizedin different ways. A sandwich construction that combines metal andnon-metal (a synthetic material, a carbon-fiber fleece or similar) isalso suitable as a material for the penetration-inhibitingreinforcement. The advantage of a polymer is the comparatively lightweight, though the cost is higher.

In a preferred embodiment, the reinforcement envelops the side walls ofthe tank all-round at a distance, and is fastened to the tank via aplurality of fastening elements. By virtue of the penetration-inhibitingreinforcement being fastened to the installation at a distance via aplurality of support points, no effect occurs at a specific point of thetank wall, and an energy-absorbing action is instead achieved. Themissile energy that strikes the outside of the reinforcement is nottransferred to the liquid inside the tank directly at the point ofimpact, and instead only a portion of this energy is transferredrespectively over a plurality of support points in a distributed manner.The pressure wave spreading in the cooling and insulation liquid isconsequently less intense. If the pressure wave hits a protective device(e.g., a Buchholz protective device or a decompression valve), there isless transformer of Figresult in an unwanted shutdown of theinstallation. By virtue of fastening the reinforcement to the outsiderather than the inside of the tank, a range of advantages are produced.Firstly, the protection can be assembled subsequently. Secondly, thearmor does not initially increase the external dimensions of theinstallation. Additionally, the armor plates can be manufactured andtransported separately. For large power transformers in particular, itis particularly advantageous for the armor to be assembled once at theoperating site, thereby facilitating the transportation through urbanareas and tunnels, the limits of the transportation already beingreached today as a result of the dimensions.

It is also advantageous that a transformer or inductor that is alreadyin operation can be upgraded with comparatively little technical effort.The attachment of the armor to the outside can easily be effected atexisting strengthening elements and tank ribs.

With regard to the manufacturing costs, in an advantageous embodiment,the bullet-proof reinforcement is made of a plate consisting of acarbon-rich hardened steel, where the plate has a tensile strengthR_(m)>1000 megapascal. It is advantageous in this case for the plate tohave a Brinell hardness of 300-500. If a corresponding protectivecoating is applied, the protective shell made of plates can also beweather-resistant. Results of ballistic trials have shown that a VPAMtest level 12 and even higher can readily be realized at reasonable costfor a power transformer.

In a particularly preferred embodiment, the penetration-inhibitingreinforcement can be made of individual plates or panels, where adjacentpanels overlap each other. As a result of the armor being made ofindividual parts, the dimensions are reduced and handling andtransportation are easier. Stock keeping is likewise simpler. In theevent of actual bullets or effects of fragments, damaged panels caneasily be replaced. The individual plates can be multilayered andcomprise metallic and non-metallic layers.

The panels can advantageously be so assembled as to stand verticallylengthways and parallel to each other. As a result, fewer fasteningelements are required between panel and installation or transformer.

In a particularly preferred embodiment, each panel has a profile, e.g.,a U, S, Z, V or C profile, where adjacent limbs interlock. A profileincreases the moment of resistance and inertia. In comparison with awelded seam, there is no material weakening and no distortion. In thecase of bullets from automatic weapons, the “multi-hit” properties areimproved. In this case, the U, S, Z, V or C profile can be so designedin cross section that the limb parts of such a profile form an obtuseangle with the connecting center part. The arrangement of the panels inthe assembled state is selected so that adjacent panels interlock withtheir limbs. This interlocking ensures that no missile or fragmentstructures can penetrate between panels and damage the tank wall. Inorder to limit the emission of operating noise, advantage can be gainedfrom ensuring that adjacent panels do not abut each other directly, anda gap is left between them instead.

In a preferred embodiment, a bracket part is used on the tank sideand/or panel side to fasten each panel, where the bracket parts are eachconnected via a spring element. The spring element has an elasticallyyielding action, whereby the kinetic energy of a striking missile or afragment is not carried directly into the interior of the liquid-filledtank. The amplitude of the shock wave propagating in the cooling orinsulation liquid is therefore lower. Unwanted triggering of a safetydevice is prevented.

An economical design of a fastening device can be constructed such thata spring element, e.g., either a metallic spring or an elastomericmaterial, is arranged between the two bracket parts. A rubber can befastened by adhesion to corresponding metal parts on both sides byvulcanization. Such vibration-damping metal-rubber-metal components arecommercially available.

Depending on the embodiment of the transformer or the inductor, domeswith high-voltage ducting and/or other parts of the installation may bearranged on the tank lid for the purpose of electrical connections. Inorder to also protect these installation parts, to the extent that theylie in the field of projection or field of view of the surroundingterrain of the installation, provision can be made for the verticallyarranged panels at their upper ends to extend beyond these domes and/orinstallation parts. As a result, these high-lying installation parts arealso protected against bullets and the effect of fragments from thesurrounding terrain.

Embodiments of transformers also exist in which the lid of the tanksupports a comparatively large expansion vessel, which extends beyondthe ground plan of the transformer tank at the side. In order to alsoprotect this expansion vessel against bullets and the effect offragments, in a particular embodiment of the invention the surface ofthe expansion vessel is likewise surrounded by a penetration-inhibitingreinforcement or armor, at least to the extent that no damage issustained in the event of an attack from the surrounding terrain.

It is also an object of the invention to provide a method for upgradingan electrical installation, e.g., a transformer, a phase shifter or aninductor. In this case, the side walls of an installation that isalready in operation are fitted with a penetration-inhibitingreinforcement. The bullet-inhibiting reinforcement is fastened to thetransformer or inductor as an upgrade by means of fastening elements, adistance being maintained all-round between side walls andreinforcement. The intermediate space formed thereby can be filled orlined with a damping material for the purpose of damping operatingnoise.

Other objects and features of the present invention will become apparentfrom the following detailed description considered in conjunction withthe accompanying drawings. It is to be understood, however, that thedrawings are designed solely for purposes of illustration and not as adefinition of the limits of the invention, for which reference should bemade to the appended claims. It should be further understood that thedrawings are not necessarily drawn to scale and that, unless otherwiseindicated, they are merely intended to conceptually illustrate thestructures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the invention further, reference is made in thefollowing part of the description to drawings from which furtheradvantageous embodiments, details and developments of the invention canbe derived based on a non-restrictive exemplary embodiment, in which:

FIG. 1 shows a perspective view of a transformer whose tank side wallsare enveloped by a penetration-inhibiting reinforcement in accordancewith the invention;

FIG. 2 shows the transformer of FIG. 1, in a viewing angle obliquelyfrom below to the radiator attached at the front side;

FIG. 3 shows the transformer of FIG. 1, in a plan view;

FIG. 4 shows an embodiment of the invention, in which the reinforcementis formed by individual vertically arranged panels as per detail X fromFIG. 3;

FIG. 5 shows an exemplary embodiment of a fastening of the panels to thetank in accordance with the invention; and

FIG. 6 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a perspective view of a bullet-resistant electricalinstallation, illustrated using the example of a power transformer 1.Here, the power transformer 1 is standing on a base which is notillustrated in detail. In accordance with the illustrated exemplaryembodiment, the penetration-inhibiting reinforcement or armor 4 envelopsthe side walls of the power transformer 1 and extends down to theground. With respect to its structure and dimensions, the armor 4 isconstructed to withstand a threat of bullets or fragments coming fromthe surrounding terrain, such that all parts of the installation areprotected. In the exemplary embodiment illustrated in FIG. 1, thisreinforcement or armor 4 consists of individual plates or panels 7 thatform a vertical protective wall. This row of successive plates 7completely surrounds the installation 1, and form a protective shellthat provides protection against bullets and effects of fragments. Theindividual panels 7 are made of steel plate whose tensile strength R_(m)is >1000 megapascal. The plate thickness complies with the intendedrating (UL 752) or test level (VPAM April 2006). The length of theindividual panels 7 is dimensioned such that any effect of bullets orfragments coming from the surrounding terrain is not able to inflictdamage on the transformer 1 or those installation parts situated on thetank lid. As illustrated in FIG. 1, the individual panels 7 thereforeextend at their upper ends beyond the installation components arrangedon the tank lid, such as lower parts of high-voltage ducts and domes 10or other installation parts of the power transformer 1.

FIG. 2 shows the power transformer 1 as illustrated in FIG. 1, likewisein a perspective view but this time seen from behind and obliquelybelow. For the removal of operating heat, the power transformer 1 has aradiator 16 on a longitudinal side. The view in FIG. 2 is directed atthis radiator 16 from obliquely below. The radiator 16 is likewisearmored on the outside and protected against destructive lateraleffects. Although a vertical cooling channel in the region of theradiator 16 is left open for the purpose of cooling, this is alsoexternally screened by panels 7 in a projectile-proof and fragment-proofmanner.

FIG. 3 shows the power transformer 1 of FIG. 1 in a plan view. Theradiator 16 is situated on a long side wall of the transformer 1. Theconnection to the energy supply network is made via high-voltage ductsand domes 10 that are arranged on the roof of the tank 2. An expansionvessel 15 is also situated on the lid of the tank 2. The expansionvessel 15 has the shape of a cylinder. The lateral surface of theexpansion vessel 15 lies approximately parallel with the plane of thetank lid. An end face of the cylinder extends beyond the ground plan ofthe transformer tank at the side. As illustrated in the drawing of FIG.3, not only the tank 2 but also the surface of the expansion vessel 17,i.e., its lateral surface and end faces, is covered by armor 4. Thisarmor 4 can likewise be composed of individual panels 7. The panels 7are arranged vertically and horizontally in this case.

FIG. 4 shows a detail X of FIG. 3 in a magnified illustration. Apreferred profile and arrangement of the individual panels 7 is depictedby way of example. The panels 7 are arranged vertically and one besidethe other. The panels 7 overlap each other laterally. Each panel 7 isconnected by a plurality of fastening elements 5 to the tank 2 or to aside wall 3 of the tank 2. The fastening can be anchored either directlyto the tank wall 3, or to ribs or strengthening elements 19 of the tank2. The individual panels 7 of the reinforcement 4 are arranged so as tosurround the tank wall 3 at a distance 6. The fastening elements 5,which are described in greater detail below, are situated in acircumferential intermediate space 18 that is delimited by the tank wall3 and the facing inner side of the panels 9. As illustrated in FIG. 4,in a preferred embodiment, the panels 7 have a U-shape profileconsisting of two limb parts 9 and a connecting part 8. The limb parts 9are bent up relative to the connecting part 8 that connects them, andwith the connecting part 8 each form an obtuse angle. In this way, thearrangement is selected such that adjacent panels 7 present a mirrorimage to each other with respect to their cross section. Limb parts 9interlock in this arrangement. A gap is left in this case. The gap andthe shape of the curve of the limb 9 are dimensioned such that a quasilabyrinth is formed. This labyrinth prevents penetration, in the regionof the point of impact, by a bullet or fragment body that has been shotfrom the external environment 21. If a fragment or a projectile strikesone of the panels 7, the attachment of the fastening elements 5 ensuresthat the energy of the missile is distributed over a plurality offastening points. Each panel 7 is supported by a plurality of supportpoints on the tank 2. The pressure wave that spreads in the cooling andinsulation liquid 22 in the tank interior 20 is therefore less intense.It is thereby possible to avoid an unintentional shutdown of theinstallation due to the effects of bullets or an external explosion. Thesupply of electrical energy in a distribution network is maintained inthe event of a destructive attack. If panels are seriously damaged, theycan easily be replaced.

The illustration of FIG. 4 also shows a hinge 14, whereby the panel 7′can be swiveled (rotated) away from the transformer tank 2 as per thearrow. By virtue of this ability to swivel one or more of the panels 7′,equipment or externally mounted parts 23 that are situated in theintermediate space 18 between reinforcement 4 and tank wall 3 can beaccessible from the outside. Such equipment 23 may comprise a displayunit, a switch unit or a connection device, for example.

A panel 7 can have a width ranging from 20 cm to a number of meters. Thehinge 17 can extend over the whole height or only a section of theheight.

FIG. 5 shows a possible configuration of the fastening device 5 forfastening the panels 7 to the tank 2. The panels 7 are fastenedvertically and at a distance 6 relative to the tank wall 3. Anintermediate space 18 is provided between the tank wall 2 and a panel 7.By way of example, a fastening with two fastening elements 5 isillustrated in FIG. 5. Here, the upper and lower fastening elements 5consist essentially of a metal-rubber-metal component that is fastenedby a bracket 10 on the tank side and a bracket 11 on the panel side tothe tank wall 2 and the panel 7, respectively. In the exemplaryembodiment illustrated here, the upper fastening structure 5 is arrangedhorizontally and the lower fastening structure 5 is arranged vertically.This makes assembly easier, because the panel 7 is hooked on at thebottom and then fastened at the top by a screw connection, for example.The panel 7 is thereby isolated from the tank 2 with respect tovibration. A spring steel can also be used instead of rubber forisolation and fastening.

In order to reduce operating noise, the circumferential intermediatespace 18 illustrated in FIGS. 4 and 5 can be filled with a noise-dampingmaterial.

Although the invention is illustrated and described in detail above withreference to preferred exemplary embodiments, the invention is notrestricted to the examples disclosed herein. Other variations may bederived therefrom by a person skilled in the art, without therebydeparting from the scope of the invention.

For example, depending on the size of a power transformer or aninductor, it may be advantageous to fasten each panel 7 to the tank 2with a plurality of fastening points. It should be appreciated theexisting strengthening elements or ribs on the tank 2 can be used orshared for the purpose of fastening.

Suitable fastening means can preferably be provided already via a weldedconnection during the manufacture of the tank. In the exemplaryembodiment illustrated, a panel 7 consists of a single steel platehaving a high tensile strength. However, non-metallic materials can alsobe used to keep any effect of bullets or explosion away from the tank.It is conceivable for the panels 7 to be sandwich panels, made of acomposite material of metal and synthetic material. It is alsoconceivable to solely use a polymer material for the armor 7, thisconsisting of, e.g., individual panels 7 of synthetic material. Thearmor 4 is then lighter in weight but also more expensive. For example,the synthetic material panels 7 can be made of the aramide fiberKevlar®, or a high-performance polyethylene (HPDE) or another suitablepolymer.

The invention is not restricted to the power transformer describedabove, but is applicable generally to electrical installations in energysupply networks, e.g. high-voltage switches which are operated usingprotective gas or similar installations.

FIG. 6 is a flowchart of a method for upgrading an electricalinstallation comprising a liquid-filled tank (2) having side walls (3).The method comprises attaching a penetration-inhibiting reinforcement(4) to the side walls (3), as indicated in step 610. Next, the sidewalls (3) are fastened to the tank (3) via fastening elements (5), asindicated in step 620. The side walls (3) are now enveloped all-round ata distance (6), such that at least the liquid-filled tank (2) and, ifapplicable, installation parts arranged on a lid of the liquid-filledtank are protected against effect from bullets and fragments, asindicated in step 630.

While there have been shown, described and pointed out fundamental novelfeatures of the invention as applied to a preferred embodiment thereof,it will be understood that various omissions and substitutions andchanges in the form and details of the methods described and the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

What is claimed is:
 1. An electrical installation, comprising: afluid-filled tank having side walls; wherein one of (i) the side wallsare formed penetration-inhibiting manner and made of a material having atensile strength greater than 1000 MPa for protection against effects ofat least one of bullets and fragments and (ii) a penetration-inhibitingreinforcement made of such a material is provided and envelops the sidewalls on the outside for protection against the effects of at least oneof the bullets and fragments.
 2. The electrical installation as claimedin claim 1, wherein the electrical installation is one of a transformer,a phase shifter and an inductor.
 3. The method as claimed in claim 2,wherein a noise-damping material is arranged in an intermediate spaceformed by the penetration-inhibiting reinforcement which is attached tothe side wall at the distance.
 4. The method as claimed in claim 2,wherein the electrical installation is one of a transformer, a phaseshifter and an inductor.